Why medicine work at time and other days it does not

I have extremely bad ankylosing spondylitis. over the years, I had been on many medications, the most recent med is REMICADE which works like a charm. long stories short, I been out of Remicade for a few months. In the pass, a doctor has given me Mobic and Celebrex before. since I am not on Remicade, I as able to obtain some Mobic. for some reason, Mobic does not seem to work the way it did before, some days when I take mobic, it works like a Charm, but some days I am in extreme pain. I also purchase some over the counter arthritis pain relief medicine, but I'm not taken much of it. the question I have is why does medicine work will one day and other days, it does not work at all? Thank you very much.

Dear friend,
Well we really can't predict the outcome of a medicine. It takes it's natural course. It's due to the same reason as how one medicine is a boon at a particular time to that patient and at the same time be causing allergic reaction.
I hope you understood my point.
Feel free to discuss more.
Regards..

The Content on this Site is presented in a summary fashion, and is intended to be used for educational and entertainment purposes only. It is not intended to be and should not be interpreted as medical advice or a diagnosis of any health or fitness problem, condition or disease; or a recommendation for a specific test, doctor, care provider, procedure, treatment plan, product, or course of action. Med Help International, Inc. is not a medical or healthcare provider and your use of this Site does not create a doctor / patient relationship. We disclaim all responsibility for the professional qualifications and licensing of, and services provided by, any physician or other health providers posting on or otherwise referred to on this Site and/or any Third Party Site. Never disregard the medical advice of your physician or health professional, or delay in seeking such advice, because of something you read on this Site. We offer this Site AS IS and without any warranties. By using this Site you agree to the following Terms and Conditions. If you think you may have a medical emergency, call your physician or 911 immediately.